1. Field of the Invention
The invention relates respectively to a driveable ground-compaction device and a ground-compaction system having several driveable ground-compaction devices.
2. Description of the Related Art
Ground-compaction devices are known inter alia in the form of remote-controllable vibration plates, in which an oscillation or unbalance exciter not only produces the vertical oscillation of the plate as required for ground-compaction purposes but also effects propulsion by means of suitable adjustment facilities in the oscillation exciter. The steering capability is achieved by the generation of directed oscillations outside a vertical axis of the vibration plate. Vibration plates of this type typically comprise two parallel unbalanced shafts which rotate in opposite directions (hence the term “dual-shaft exciters”), wherein one of the shafts supports two axially disposed unbalanced masses which can be adjusted independently of each other in their relative phase position. The sum of the m·r values (m=unbalanced mass, r=eccentricity of the centre of gravity of the unbalanced mass) of these unbalanced masses corresponds to the m·r value of the second exciter shaft which likewise supports an unbalanced mass but rotates in the opposite direction. By appropriately synchronising the phase angles of the three unbalanced masses it is possible to produce oscillations directed in a known manner. This type of oscillation exciter is known from DE-G 78 18 542.9.
If the resulting force vector of the oscillations are forwardly inclined in the direction of travel of the vibration plate, the machine will be accelerated forwards. When negotiating a turn to the left, the left-hand unbalanced mass of the shaft, which supports the two unbalanced masses, is synchronised with the large unbalanced mass of the other shaft in such a manner that the force vector resulting from the three rotating unbalanced masses generates a turning moment (yawing moment) about the vertical axis of the vibration plate. Appropriate synchronisation of the unbalanced masses also renders it possible to adjust any so-called standing vibration, in which the resulting force vector is directed in a vertical direction. Accordingly, it is also possible to carry out reverse travel or rotation of the vibration plate in a standing position.
The vibration plate is controlled typically by means of electromechanical or electrohydraulic actuators for the relative rotation of the unbalanced masses which actuators are actuated by means of radio, infrared or cable remote-control.
By reason of the tumbling jumping movement of the vibration plate dragging partly on the ground during the vibration operation, constantly changing forces and turning moments are transmitted to the driveable vibration plate depending upon the condition of the ground and the coefficient of friction between the plate and the ground. A low constancy of direction during operation of the vibration plate results, so that in short time intervals the operator is required to correct the direction of movement, in order to prevent the vibration plate from swerving. To this end, it is conventional in the case of remote-controlled vibration plates to stop the vibration plate and whilst at a standstill to rotate it about the vertical axis by the generation of a maximum yawing moment. Although it is possible, in principle, to negotiate a turn, i.e. to generate a yawing moment during the simultaneous propulsive movement of the vibration plate, the low degree of directional stability makes this scarcely feasible in practice. The continuous alignment of the vibration plate requires the operator's utmost concentration.